Cathode-ray oscillograph



Dec. 31, 1940.

KNOLL QATI'IODE-MY OSC-ILLOGRAPH Original Filed Feb. )5. 1955 INVENTOR. MHKKNQLL A TTORNE Y.

Patented Dec. 31, 1940 UNITED STATES CATHODE-RAY OSCILLOGRAPH Max Knoll, Berlin-Charlottenburg, Germany, assignor to Radio Corporation of America, New York, N. Y., a corporation of Delaware Original application February 5, 1935, Serial No. r

5,136, now Patent No. 2,152,487, dated March 28, 1939. Divided and this application June 7; 1937,

Serial No. 146,967. 1928.

3 Claims.

This invention has for its object improvements in cathode-ray oscillographs, and is a division of Patent No. 2,152,487, issued March 28, 1939, and relates in subject matter to application, Serial No.

5 5,136, dated February 5, 1935.

More particularly, this invention relates to a new method and means for electrostatically focusing a beam of electrons in a cathode ray tube.

In describing the invention, reference will be made to the drawing, in which is shown a cathode ray tube embodying the invention connected in a circuit for automatically starting electron flow in response to transmission line surges by way of example.

The tube 32 for auto-electronic discharge shown in the drawing contains an anode 33 and an intercepting electrode (auxiliary anode) 34 which during the release of the beam functions as an anode. The release is effected by two spark gaps or glow-lamps 35 and 36 connected by way of windings 31, 38 with the perforated intercepting electrode 34 and by way of a high resistance element 39 with the cold cathode 4B. The hightension continuous current required for feeding the tube is generated in the known manner by means of transformer 4|, valve 42, and condenser 43. If the gaps 35 and 36 are properly adjusted, any sudden surge of voltage arising from the transmission line or antenna 44 and inducted from the winding 45 according to the polarity of the surge, either onto the winding 31 or 38, causes a sparking of the gap or 36, the duration of which depends upon the value of the capacity 46 and the resistance 41. By this the elec- 35 trode 34, which has hitherto intercepted the beam, becomes an anode, and the extremely sharp point of the cathode ejects an electronic beam through the perforations in the electrodes 34 and 33, the intensity of the beam can further be "var- 40 led by means of the controlling electrode 33 by varying the angle of the cone-shaped electronic beam.

The focussing of the electron rays as required for the oscillograph according to the present invention, can be effected in the known manner e. g. by magnetic fields. A new arrangement, especially convenient for the purpose in view, based on electrostatic effect, consists in fixing, at certain intervals from one another, co-axially with,

and symmetrically to, the electronic beam ejected by the cathode, pairs of electrodes of suitable form (e. g. alternately perforated metal cylinders with small, and washers with large, diameter), which are connected alternately with appropriate 65 voltages. In this way there are produced diver- In Germany December 12,

gent electric fields with a stress acting obliquely tothe direction of the beam, in such a way as to compress the beam'gradially. If the voltage is sufficiently high, one single pair of electrodes. may suffice to effect this concentration. The di- 5 vergent fields can be obtained by various types of electrode. If a. controlling voltage is. supplied to such a device, the intensity of the electrons in the beam, and thereby the intensity of the focal spot, can be varied without inertia. The es- 10 pecial advantages of this arrangement are: ease in construction and mounting, small weight, small dimensions, and avoidance of consumption of current.

With the alternate voltage connections made 15 such that all the cylinders will be positive and all the washers negative, a series of divergent electric fields acting to compress the beam may be produced without necessity for progressively increasing voltages on the electrodes. In fact 20 alternate electrodes may have the same polarity regardless of their number and their position in the series, as indicated in Fig. 6, which makes it possible to connect them in multiple, thus simplifying the wiring and insulation problems. An- 25 other advantage is that focusing may be acccomplished without undue increase in velocity or hardness of the beam which latter would tend to render the beam less sensitive to deflectioncontrol. It will also be clear from Fig. 6 that this 3 method of focusing also permits variation of the intensity of the electrons in the beam and thereby the intensity of the focal spot without undue disturbance of the focus, such variation being accomplished by supplying a controlling voltage 35 to the focusing device as above mentioned, variations in the controlling voltage acting to correspondingly vary the forces exerted radially on the cathode-ray and consequently the density of the electrons within the focal spot. Any known 40 or other suitable method of applying the controlling voltage may be used.

In the lower part of the figure is shown schematically an electrostatic device for concentrating the electronic beam in accordance with 45 the method above described. It consists of relatively narrow cylindrical metal tubes 48 of substantially uniform diameter from end to end, sustained by supports 49 in such a position as to allow of the electronic beam to pass so freely through them, and of the metal ring washers 50 of relatively large inside diameter between the tubes 43. If the washers 50 are charged negatively to the tubes 48, divergent electric fields are formed, which exercises a force concentrating radially the beam. Thus an exceptionally minute focal spot is obtained.

What I claim is: v

1. In a cathode my device, an electron emitting cathode and an anode member for producing a beam of electron rays, a target element, and means intermediate the cathode and the target for concentrating the electronic beam, said concentrating means comprising alternate metal tubes and ring washers arranged in sequence concentric with the beam, each tube spaced longitudinally from a preceding washer and each washer spaced longitudinally from a preceding tube axially of the beam, said tubes having an. inside diameter smaller than the inside diameter 7 of said washers, and means for maintainingthe washers charged negatively to the tubes to form a sequence of alternate oppositely polarized clivergent electric fields.

2. In a cathode ray device, a cathode and an anode for producing a beam of electrons, means in addition to the anode situated in the path of the beam beyond the anode for concentrating the electronic beam in a focal spot comprising divergent electric field.

a tube and a ring washer longitudinally spaced in the tube, the ring washer having an inner diameter larger than the inner diameter of the tube and arranged coaxially with the beam, means for applying a voltage between the washer and the tubefor maintaining the washer charged negatively with respect to the tube to form a 3. Means for producing a focussed cathode ray beam comprising means for producing a cathode beam and focussing means in the path of the beam separate from and beyond the beam' producing means comprising a plurality of annular conductors of which at least one extends longitudinally of the beam axis for a length at least greater than the inner diameter of the annulus, each of said conductors being longitudinally spaced from an adjacent conductor oneach side axially of the beam, and. means for maintaining a difference of potential of alternate polarity between said conductors to produce alternate de celerating and accelerating electrostatic fields.

MAX KNOLL. 

